ABSTRACT
Although DSS has been classically considered a congenital malformation there are many patients who acquire the disease later in life without any former evidence of predisposing substrate. Indeed, although more frequently in youth, DSS may be diagnosed at any age. In addition, progression in hemodynamic severity after diagnosis may or may not develop, and we do not know yet why, when, and how it may happen. Certain observations on the follow-up of patients have shown another possible evolution of the disease, from a thin membrane to a more advanced muscular type. So, as postulated by Somerville over 25 years ago,4
the pathologic basis seems to reside in the myocardium which could generate, by unknown mechanisms, a wide spectrum of abnormal hypertrophic responses in the left ventricular outflow tract.
